Piston for internal combustion engines



13, 1964 M. cs. WHITFIELD ETAL 3,152,523

PISTON FDR INTERNAL COMBUSTION ENGINES Filed Aug. 16, 1962 2Sheets-Sheet l BY Ham-3 Wesldke A6EN7' Z0 INVENTORS Mars\na1l GWhLH'LelcL- Oct. 13, 1964 M. a. WHITFIELD ETAL 3,152,523

PISTON FOR INTERNAL COMBUSTION mamas Filed Aug. 16, 1962 2 Sheets-Sheet2 INYENTORS United States Patent 3,152,523 PISTON FOR INTERNALCOMBUSTION ENGINES Marshall G. Whitfield, hrookfield, Conn. WhitfieldLaboratories, Inc., R0. Box 293, Bethe Conn.), and Henry Weslalre,Harbour Road, Rye Harbour, Sussex, England Filed Aug. 16, 1962, Ser. No.217,416 3 Claims. (Cl. 92-213) This invention relates to pistons forinternal combustion engines, and more particularly to pistons for usewith engines of the type employing fuel injection.

In internal combustion engines of this type, pistons which were madeentirely of light metal such as aluminum or aluminum alloy, have notproved to be satisfactory, due in large part to the erosion caused bythe fuel injection into the cylinders. In some instances the light metalof the piston was actually melted, particularly where the hottest areaexisted at the top or head, resulting in early failure.

In the past various proposals have been made to remedy this problem,such proposals involving the use of head caps, inserts or facings of aharder material or metal, intended to withstand the high temperatures.In the case of inserts, these were located in the path of the injectedfuel, to bear the brunt of the impingement thereof on the piston head.

While the above arrangements were of some service, they have not beenfully satisfactory to the extent of meeting all of the requirements forthis particular use. The construction Where the entire top of the pistonwas covered with a ferrous metal body or cap proved disappointingprimarily because of loosening and separation of the top portion,although excessive heat transmission to other areas also resulted in adistinct disadvantage. Accor ingly, for the most part, pistons whichwere made entirely of iron have generally been employed in this type ofinternal combustion engine.

The matter of heat transmission above mentioned constit-uted animportant further drawback of these prior constructions, becauseappreciable amounts of heat were conducted from the piston head or capto the cylinder block, the lubricating oil, and the associated pistonparts.

The above drawbacks and disadvantages of prior piston constructionsintended for this purpose have been obviated by the present invention,and one object of the invention is to provide a novel and improvedmulti-part or multielement piston for the indicated and similar uses,which results not only in a lighter construction but also a greatlyprolonged service life together with an appreciable reduction in heattransfer from the combustion area.

A further object of the invention is to provide an improved multi-pa-rtor multi-element piston construction as above set forth, which resultsin lower oil temperatures, lower bearing loads and temperatures, and ina simplified pin-bearing structure.

An additional object of the invention is to provide a novel pistonconstruction as characterized for the above and similar uses, wherein arugged heat-insulating metal as titanium or its alloys is combined witha light metal in such fashion as to attain the above objects and at thesame time prevent failure from loosening and separation of theconstituent parts, which condition has hitherto adversely affectedservice life.

These and other objects of the invention, which will be set forthhereinafter or will be apparent to one skilled in the art upon readingthese specifications, are accomplished in that structure and arrangementof parts, of which certain exemplary embodiments will hereinafter bedescribed. Reference is made to the accompanying drawings wherein:

FIG. 1 is a plan view of a piston from the head end with a part insection, the section being taken transversely at a position just abovethe pin boss.

FIG. 2 is a side elevation of the piston with certain parts in section.

FIG. 3 is a vertical sectional view of the piston taken along thesection line 1-1 of FIG. 2.

FIG. 4 is an elevational view of a modified form of piston with parts insection.

FIG. 5 is a partial elevational view of a piston somewhat modified fromthe showing of FIG. 4.

FIG. 6 is a top plan view of a composite piston structure, constitutinganother embodiment of the invention.

FIG. 7 is a fragmentary sectional view of the composite piston structureof FIG. 6, taken on the line 77 thereof.

FIG. 8 is a fragmentary axial sectional view of a composite piston,illustrating a ring groove reinforcement as provided by the invention.

In the specifications which follow, the term titanium will be used todesignate portions formed of titanium and its alloys. These portions areprefabricated structures, which may be made by casting, forging or thelike, and which are located in molds for the casting of the light metalagainst them. The term light metal is used herein to designate aluminumand aluminum alloys.

Briefly, in the practice of the invention, a heat-insulating, abrasionand heat resistant head or ring section of titanium metal is provided,which head has portions extending downwardly along the cylindrical sidewalls of the piston to a point well above the pin bosses, but ofsufiicient depth to encompass at least the upper one of the piston ringgrooves. The depending portion of the titanium metal head is dividedcircumferentially by grooved or other configurations into a plurality ofparts between which the light metal may flow upon casting. The head hasan upper surface shaped as desired but usually concave in configurationto coact with the fuel injection jet. The top portion of the head orca-p may be relatively thin. In a prefenred embodiment it is providedwith downwardly extending bosses, the shape and purpose of which willhereinafter be described.

After suitable treatments hereinafter described, the head or ringelement will be placed in a suitable mold and the light metal castagainst it to form the remainder of the piston structure. The moldingmay be done in sand molds or in permanent molds, as desired. The headmay be provided with one or more extensions for the purpose of locatingit accurately in the mold, and these extensions will be removed when thepiston is finished. The finishing is done conventionally by surfacingthe cylindrical side walls of the piston including the heavy metal andlight metal portions, in a turning operation, accompanied by the millingof the piston ring grooves.

Referring now to FIGS. 1, 2 and 3, there is shown as provided by theinvention a piston having a head portion or cap 2 of heat-insulating andheat-resistant titanium metal or alloy. This head has a central topportion 3 of suitable configuration and a relatively heavier rim portion4 having a depending part 5 of substantially the same thickness. Thedepending portion of the head is in this instance divided into aplurality of portions 6 by a series of radially disposed slots 7, asillustrated.

The head or ring section is placed in a suitable mold and the lightmetal is cast against it. It is advisable to make provision for asuitable bond between the light metal of the body and the titanium metalof the head cap or ring section. In one procedure, the cleaned head iselectrically coated with tin to a thickness of about .0002 in., more orless. In the casting operation the mold is so constructed and thepouring is accomplished in such a way that the molten metal flows pastthe surfaces of the ferrous metal body against which it is cast for asubstantial interval, carrying away oxides and impurities. In thisprocedure a sound bond is produced with a minimum of interface alloy,and in many instances no visible interface alloy. In another procedure,the titanium head or ring section may be directly dip coated in a moltenaluminum bath unti it is wetted with aluminum, than transferred to amold wherein additional aluminum or alloy are cast to make the casting.Or, a bonding procedure may be employed as set forth in U.S. Patent No.2,785,451, which involves titanium and aluminum.

The precise shape and dimensions of the piston form no limitation on theinvention, as will be understood, and may be varied in accordance withdifferent designs for different services. The light metal will underliethe central portion of the head, as shown at 15. It will also lieinwardly of the depending portions of the head, as at 16, being thickenough to impart sufficient strength and rigidity to the upper part ofthe piston. The piston will normally have a skirt portion 17 which isrelatively thinner and may be as long as required by the particulardesign. The piston will be characterized by openings 18 in which thewrist pin is engaged, these being provided with the inwardly exxtendingwrist pin boss 12. It is usual in the design of many pistons to connectthe wrist pin bosses with the upper part of the piston by relativelythickened portions or wrist pin ribs 19 which may have a variety ofshapes.

In casting the light metal against the head or ring section, i.e.between the head, outer mold walls, and a suitable core element orelements, the molten light metal will coat the entire interior portionof the head, and be bonded thereto, and will flow into the interstices 7between the downwardly projecting elements of the head. An interlockeddesign is thus produced in addition to the bonding aforesaid.

A modified form of structure is shown in FIG. 4 in which like parts havebeen given like index numerals. Here the downwardly projecting portionof the head has been divided into spaced extensions 20 which arepreferably so shaped as to provide downwardly converging portions 21terminating in end enlargements 22. This not only minimizes weight for agiven downward extension of the head, but also provides an anchoringstructure, as will be evident.

Additionally, it is preferred to provide the central head portion 3 withdownward extensions 23, of which three have been shown in FIG. 4,although more may be provided as will readily be understood. In asymmetrical construction in accordance with the design of FIG. 4, therewould be five such downward extensions. The downward extensionspreferably comprise head portions connected to the top of the pistonhead by necks of relatively smaller cross sectional dimensions, and areroughly mushroom shaped. This provides a structure in which thermalstresses in one direction are offset by thermal stresses in the oppositedirection, whether under the particular thermal conditions the lightmetal or the heavy metal is expanding more rapidly. The reduction inarea also relieves stress on the bond. The cap remains tight at alltimes during the operation of the engine.

In the structure of FIG. 4, the upper piston ring groove 24 is formedentirely in the downward projection of the head. The groove 25 in thisinstance is formed partly in the downward head extensions Zti and partlyin the light metal body of the piston. In PEG. there is shown amodification in which the spaces between the extensions 20 are carriedupwardly so as to cut the upper piston ring groove 24-. The anchoringaction is the same, but a still further saving in Weight is effected.

Another embodiment of the invention is illustrated in FIGS. 6 and 7,wherein the head cap and ring section 26 has a diiferent, particularconfiguration providing a head cavity 27 found to be desirable forutilizing to the fullest extent the fuel injection characteristic ofcertain combustion engines. As shown in this figure, the head cavity 27is circular or cylindrical, and nonconcentrically disposed in the cap,the eccentricity being evident from the spaced centers 28 and 29 of thecavity and cap respectively. By such eccentricity the cavity may belocated at the most advantageous point with respect to the injectedfuel, to receive and distribute the latter. Further, the cap is providedwith angularly extending tangential holes or passages 30 in the mannershown in the section of FIG. 7. These holes are of number, angle anddiameter to suit the particular head cavity in use. Upon compression inthe engine, the rapid air movement through these passages causes aviolet rotational movement or swirling of the air in the cavity 27,which promotes more complete and faster combustion.

The presence of the passages 30 also tends to oppose localized attack onthe piston crown or cap by high temperature gases, owing to thealready-mentioned swirling characteristic. During the combustion, thepath of the burning gases passes from the cavity to the squish orperipheral areas of the piston via the tangential passages 30. Thus, inconjunction with the titanium metal of the cap 26, the cavitatedconfiguration of the top surface portions thereof enables high enginetemperatures to be successfully withstood. The combination is effectiveand advantageous, in consequence, in accomplishing the objectives of theinvention.

Still another embodiment of the invention is illustrated in FIG. 8. Inthis figure there is shown a piston-ring groove reinforcement inset orinsert of titanium in the form of an annulus 32 having an externalannular pistonring groove 34, the said inset being joined to a pistonbody 36 of light weight metal such as aluminum, aluminum alloy orequivalent substance. Preferably, as shown, an interlocking constructionis effected between the ring reinforcement or inset 32 and the pistonbody 36, as by the provision of an internal annular groove 38 in theinset, which groove is occupied by an annular integral portion at of thepiston body. By such interlocking construction there is positivelyprevented any failure of the piston due to loosening or separation ofthe components, inasmuch as it is physically impossible, except bybreakage, to separate the interlocking parts.

The annular reinforcement or inset 32 is, in accordance with theinvention, consituted of heat insulating and heatresistant metal, suchas titanium or alloys of the same as above mentioned, which have a lowheat conductivity and and hi h melting point. Any desired configurationmay be provided at the end face 40 of the piston shown in FIG. 8, theflat surface shown being used for simplification of illustration.

From the foregoing it will be seen that we have provided a novel andimproved composite piston construction which is especially adopted andadvantageous for use with internal combustion engines of the typeemploying fuel injection. Not only does the composite piston structuresuccessfully withstand the high combustion chamber temperatures and theadverse effects of impingement of the injected fuel, but a markeddecrease of heat transmission is effected to the piston body andassociated parts of the piston, as well as the side walls of thecylinder, and to the lubricating oil. The composite piston is ofrelatively simple construction, and may be readily economicallyfabricated and produced by the procedures outlined.

Modifications may be made in the invention without departing from thespirit of it. The invention having been described in certain exemplaryembodiments, what is claimed as new and desired to be secured by LettersPatent is:

1. For use in a fuel injection internal-combustion engine, incombination, a heavy titanium metal head structure and a light metalpiston body structure carrying the head structure, said head structurecomprising a covering portion for the top of the piston body structure,said covering portion having a thickness which at the least is notgreatly less than the thinnest side wall portions of the piston bodystructure and said covering portion being constituted essentially oftitanium characterized by heatinsulating qualities which are appreciablygreater than the heat-insulating qualities of the piston body structureon which it is carried, said covering portion having a dependingperipheral skirt which is greater in wall thickness than the remainderof the covering portion.

2. For use in a fuel injection internal combustion engine, incombination, a heavy titanium metal insert and a light metal piston bodystructure carrying the insert, said insert comprising a circularstructure secured to upper portion of the piston body structure as aninsert in surface portions thereof, said insert having a thickness whichis greater than the thinnest side wall portions of the piston bodystructure and said insert being constituted essentially of titaniumcharacterized by heat-insulating qualities which are appreciably greaterthan the heat-insulating qualities of the piston body structure on whichit is carried, said insert band having an axial dimension which issubstantially greater than its thickness.

3. For use in a fuel injection internal combustion engine, incombination, a piston comprising a light metal body structure and atitanium head band structure secured to said body structure andextending circumferentially along the cylindrical side walls thereof,said band structure having an exposed edge constituting a portion of thehead surface of the piston body structure and being constituted of aheavy metal characterized by heat-insulating qualities and containingessentially titanium, said head band structure having a thickness whichis greater than the thinnest side wall portions of the piston bodystructure and the heat-insulating qualities of said band structure beingappreciably greater than the heat-insulating qualities of the pistonbody structure.

References Cited in the file of this patent UNITED STATES PATENTS

3. FOR USE IN A FUEL INJECTION INTERNAL COMBUSTION ENGINE, INCOMBINATION, A PISTON COMPRISING A LIGHT METAL BODY STRUCTURE AND ATITANIUM HEAD BAND STRUCTURE SECURED TO SAID BODY STRUCTURE ANDEXTENDING CIRCUMFERENTIALLY ALONG THE CYLINDRICAL SIDE WALLS THEREOF,SAID BAND STRUCTURE HAVING AN EXPOSED EDGE CONSTITUTING A PORTION OF THEHEAD SURFACE OF THE PISTON BODY STRUCTURE AND BEING CONSTITUTED OF AHEAVY METAL CHARACTERIZED BY HEAT-INSULATING QUALITIES AND CONTAININGESSENTIALLY TITANIUM, SAID HEAD BAND STRUCTURE HAVING A THICKNESS WHICHIS GREATER THAN THE THINNEST SIDE WALL PORTIONS OF THE PISTON BODYSTRUCTURE AND THE HEAT-INSULATING QUALITIES OF SAID BAND STRUCTURE BEINGAPPRECIABLY GREATER THAN THE HEAT-INSULATING QUALITIES OF THE PISTONBODY STRUCTURE.